Mailinglist Archive: opensuse (1695 mails)

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Re: [opensuse] 10.2 no RAID to 11.0 RAID 1
  • From: "Hylton Conacher (ZR1HPC)" <hyltonconacher@xxxxxxxxx>
  • Date: Tue, 23 Sep 2008 15:33:14 +0200
  • Message-id: <fb35d81a0809230633t78e21700w57fbd06f7e8c50d@xxxxxxxxxxxxxx>
Sorry, forgot to change the recipient email address. :(

2008/9/23 Hylton Conacher (ZR1HPC) <hyltonconacher@xxxxxxxxx>:
2008/9/23 Carlos E. R. <robin.listas@xxxxxxxxx>:
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The Tuesday 2008-09-23 at 12:27 +0200, Hylton Conacher (ZR1HPC) wrote:

No because I've already "been there" and "done that" -- It is
IMPOSSIBLE to recover a RAID-1 array that just one day (after properly
shutting down the system and not having hardware failures) decided not
to boot.

Ahhh, now this is interesting :) The main reason I was creating the
RAID1 array was so that if one drive failed, I could receive a message
from mdadm, swop out the bad drive and continue working, without
losing data.

Of course you can continue. You can even have a third disk as active spare
and the system will switch over to it without downtime.

It was only Andrew who had some problem, which at the moment is not fully
clear what it was.
Ok, Sorry Andrew, you are the bad apple in the mix :)

In view of the above comment, I guess it is time I ordered the 3rd HDD
and rather setup RAID5.

You could have the same type of problem. Both raid 1 and raid 5 can
withstand the failure of a single disk without downtime, with different
approaches. It will depend on the hardware of course, whether you can
replace the disk "hot".
Hot replacement is not necessary as long as the machine can be powered
down, not lose data, have the replacement HDD inserted, and then get
restarted and rebuild the array.

HW RAID cards are a MAJOR expense for a home hobbyist who just likes
to make sure their data is retrievablein the event of a HDD crash.

In fact, I don't think you need raid at all.
I second that as I have read that RAID is not a backup method. A valid
backup is a far better replacement for RAID in this instance.

Raid is for minimizing the downtime to zero, for systems that have to be
accessible full time. That is not usually the case for home, unless you want
to experiment. IMO it is safer to have that second disk as a full backup,
updated at least daily via rsync.
Now THAT is a SMART idea.

The backup has an advantage: you can recover from a software crash or finger
error: the other disk is not mounted, so nothing is written to it "yet". On
a raid, both copies would have the same wrong data.
The downside is that the machine is going to be a file/print/mail
server and while I may have a backup as of yesterday, if I screw up a
document, I cannot simply just restore the backup as other email would
have been added to the live mail server that would be lost if it was
restored from the offline backup.
I guess the way around that is to have two rsync jobs being one for
the mail directories and the other for only the document directories?

Tnx Carlos for the idea!

Regards
Hylton

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